1. Field of the Invention
The present invention relates to a novel ionomer composition for a golf ball, which can be preferably used for producing the golf ball, a production method thereof, and a golf ball using the composition.
2. Description of the Related Art
A wound-core golf ball having a balata cover, a two-piece or three-piece golf ball having an ionomer cover, and the like are known as a conventional golf ball. A wound-core golf ball having a balata cover has good shot feeling and controllability, but is expensive due to the complicate production steps, and also has problems such as poor durability and abrasion-resistance. A golf ball having an ionomer cover is excellent in resilience, abrasion-resistance and molding ability due to the relative hardness thereof, but has problems such as poor shot feeling and controllability.
Therefore, the improvements of the shot feeling and the controllability of the ionomer cover have been proposed, for example, in Japanese Unexamined Patent Publication Nos. H01-308577, H05-277208, H07-132152, H08-182777, H11-500776, and 2001-515529. For example, Japanese Unexamined Patent Publication No. H01-308577 discloses a technique of blending a hard ionomer and a soft ionomer. Japanese Unexamined Patent Publication No. H05-277208 discloses a technique of using 2 or more kinds of ionomer resins having a relatively low modulus. Japanese Unexamined Patent Publication No. H07-132152 discloses that a heated mixture of an ionomer resin, a terpolymer consisting of α-olefin, an unsaturated carboxylate and an unsaturated carboxylic acid, and a glycidyl group-containing α-olefin copolymer resin is used as a base resin of the cover. Japanese Unexamined Patent Publication No. H08-182777 discloses that a heated mixture of three kinds comprising an ionomer resin, a maleic anhydride-modified olefin copolymer and a glycidyl group-modified styrene-based block copolymer having JIS-A hardness of from 30-90 is used as a base resin of the cover. Japanese Unexamined Patent Publication No. H11-500776 discloses a production method of a composition for the golf ball cover, comprising saponify a polymer with an inorganic metal base to produce a polymer salt with saponification degree of about 1 to 50%, wherein the polymer comprises a first monomer component containing an olefin monomer having 2 to 8 carbon atoms, a second monomer component containing an acrylate ester having 4 to 22 carbon atoms based on an unsaturated carboxylic acid, and an optional third monomer component containing at least one monomer selected from the group consisting of carbon monoxide, sulfur dioxide, an unsaturated monocarboxylic acid, an olefin having 2 to 8 carbon atoms and a vinyl ester or a vinyl ether of an alkyl acid having 4 to 21 carbon atoms. Japanese Unexamined Patent Publication No. 2001-515529 discloses an acid copolymer such as ethylene-methacrylic acid or a composition including an ionomer and an adipic acid component.